I think it was due to multiclassing- if you go back to an early playtest, the playtest Cleric had this channel divinity style power that had it's uses tied to proficiency bonus per day and scaled based on proficiency bonus- so any character could dip Cleric 1 to get this feature and have it scale for them the same way it did for a full Cleric.
This is fine for racial abilities that are meant to scale in that fashion, but they apparently felt that for class abilities, this might open the door for multiclass shenanigans that they knew people would gripe about (and apparently declaring multiclassing as optional and telling DM's to "figure it out" was not the free pass they'd hoped it would be, lol) so they made some attempts to shove the genie back into the bottle.